Compressor control mechanism



Nov. 22, 1938. B.S. AIKMAN 2,137,219

COMPRESSOR CONTROL MECHANISM Filed Aug. 22, 1935 2 Sheets-Sheet 1 INVENTOR BURTON SAIKMAN ATTORNEY Patented Nov. 22, 1 938 2,137,219 l COMPRESSOR coN'moL. MECHANISM Burton S. Aikman, Wilkinsburg,-'Pa., assignor to The Westinghouse Air Brake Company, Wilmerding, Pa., a. corporation of Pennsylvania- Application August 22, 1935, sen-arm): 37,380

. 13 Claims; (Cl. 23044 This invention relates to a control system for a ,fluid compressor and for an internal combustion engine for driving the said compressor.

It is an object of this invention to provide a fluid compressor having unloading means associated therewith and normally operative to maintain the compressor unloaded, together with means subject to and operated upo'n a predetermined reduction in the pressurebfthe fluid'in the fuel inlet passage of the internal combustion engine employed to drive the compressorto actus ate the unloading. means toeffect loading of'the compressor. I l

Another object of theinventionis 'to provide a compressor of the'typ'e referred to and'having means responsiveto the pressureof the fluid compressed 'by the. compressor and controlling com-' munication between the engine inlet passage and the means controlling the compressor unloading means. d 1

A further object 'oi'the" invention is to provide a compressor of the'type referred to and having means responsive to t h'e speed of the compressor and controlling communication between the engine inlet passage 1and the jmean's controlling the compressorunloa'ding' means;

Another objectof theinvention is to provide a 'h'av'in g means subject to and operated upon a predetermined reduction in the pressure of the ,fiiiidinth'fuelinlet passage of the internal combustion engineem ployed to drive the compressor l, to actuate the unloading means to efiect loading lof the compressor, the fuel inlet passage having a throttle valve controlling the flow of fluid therethrough; the throttle valve being movable between an engine idling position and an engine load position', the control system being responsive to the pressure of the fluid compressed by the compressor, and being opreated upon a predetermined reduction in said pressure to move the throttle 'valve from the idling position to the load position, and to establish communication between the fuel inlet passage and the means controlling the unloading means so as to effect loading of the compressor.

' A further object of the invention is to provide a control system of the type referred to and in which the throttle valve is gradually moved from the idling position to the load position,'and in which the unloading control means is not operated to cficct loading of the compressor until the throttle valve has been moved a predetermined distance froni tlie idling position towards'fthe load-position.

another object of meinvenson is to provide an-improved control system for a fluid compressor and foraninte engine employed to drive the compressor. 3

Other 'objcts 'ofthe'invention and features of novelty will be apparent from the following descriptiori ta'ken in "connection with the" accompanying drawings in which- Fig; liis an elevational"view of a compressor and-internal-combustion engine for drivingthe compressor together with the control system provided'by myinv'ention. v Fig. 2 is a-diagrammatic view, largely in section, of the control'systemprovided by my invention,

and 1 Fig. 3 'is -afsectional view taken substantially along the line 3 -3 of "Fig.2. 1

Referringto' the drawings a fluid compressor is indicated generally by the reference numeral I, and is driven by an internal-combustion engine,

which is indicated generally by the reference character 3; and which may be well-known construction.

fThe-compre'ssor I: compresses fiuid into a reservoir-:4 by way of sa' discharge'pipe 6, while.the

of any suitable,

' engiri'e'3 is'=supplifedwith fuel from the carburetor 8 byway of -aefuel inlet-passage 9, which has, a

throttle valve-'l-nzinterposedtherein and which .ing operated by the partial-vacuum, created in the fuel inlet passage of theengine when the engine is running to permit the inlet valve to close and thus effect loading of the compressor. The control system provided by this invention provides means to control the communication between the unloading control means and the engine inlet passage, and also to control the throttle valve in the inlet passage in response to varia-- tions in the pressure of the fluid compressed by the compressor.

The control system provided by "this invention comprises a control device indicated generally by the reference numeral and which is operated by lubricant under pressure supplied thereto by the pump l4 of the compressor lubricating sys-' term. The control system includes, in addition, a

pressure responsive device |6 which is subject to close the'passages 24 and 25 which extend through the valve seat. The annular rings 22 and 23 are urged into engagement with the seat 2| by means of springs 21 which extend between the annular rings 22 and 23 and cage 28. I

The inlet valve assembly |2 includes, in addition, a body 38 having a piston chamber 3| formed therein in which is mounted a piston 32 which has secured to the lowerface thereof fingers 33 and 34 which extend into the openings 24 and 25, and which are adapted to engage the annular rings 22 and 23 to move these downwardly against the springs 21. A spring 36 is positioned in the piston chamber 3| andextends between the piston 32 and the upper wall 38 of the piston chamber 3|, and normally urges the piston 32 downwardly so that the fingers 33 and 34 force the annular rings 22 and 23 away from the seat 2|, thus maintaining the compressor unloaded.

The upper face of the end wall 38 is provided lubricatingsystem which supplies lubricant under pressure to different parts of the compressor, and as shown in the drawings, this system comprises a pump, indicated generally by the reference character l4, and which is adapted to draw lubricant from the lower or crank case portion of the compressor, which serves as an oil reservoir and forces this lubricant through suitable passages to the portions of the compressor to be lubricated.

As shown in the drawings the pump |4 comprises a piston 50, which is journaled on an ec-' centric 5| formed on the compressor crank shaft 52. The piston 50 is reciprocable in a piston chamber 55 formed in the member 56 which is pivotally mounted on the compressor-body by means of brackets 58 and 59. The piston 50 has a passage 68 extending therethrough and registering with an annular groove 6| formed in the' eccentric on the crank shaft 52, which in turn communicates with passages, not shown,

-drilled in the crankshaft and-leading to portions of the crank shaft to be lubricated.

The lower end of the passage 68 in the piston 58 is controlled by acheck valve device which,

as shown in the drawings, comprises a seat mem;

ber 63 which has a ball valve element 64 engage- The chamber 55'has an inlet passage 19 communicatingtherewith at a point spaced from the end thereof and leading. from a chamber II formed in the bracket 58, this chamber having a screen 12 extending there across and through which is drawn the lubricant which flows to the pump.

The chamber 55 has a discharge passage leading therefrom at a point adjacent the end thereof and communicating with a pressure re lease valve device indicated generally by the reference numeral 16 and comprising a valve seat member 11 having a ball valve element 18 nor mally held in engagement therewith by means of a spring 19. When the pressure of the lubricant pumped by the pump exceeds a predetermined value, the ball valve'element 18 is forced away from the seat on the member 11, thereby permitting fluid to escape by way of the passages 88 thus limiting the pressure which can be built up in the lubricating system.

The passage 15 also has a passage 85 communicating therewith through a choke or restricted portion 84 which limits the rate of flow of fluid from the passage 15 to the passage 85. The passage 85 has connected thereto a pipe 86, which communicates with the control device l5 and the fluid pressure responsive device I 6.

The control device I5 comprises a body section 98 having a bore 92 therein in which is mounted a piston 9| which is normally urged into engagement with a plug or cap member 93 by means of a spring 95 acting through a plunger 96, which is provided with a rounded end portion 91 which extends into a conical recess 98 in 'the face of the piston 9|.

The chamber Hill on the left hand side of the piston 9| is connected by way of the pipe 86 with the pump I4 of the compressor-lubricating system. The other end. of the plunger 96 is connected controls. the throttle valve I0 in the fuel inlet passage 9 of the engine 3, as is best shown in Fig. 1 of the drawings. A

The control device |5'also includes a body section ||8 which has formed therein a valve chamber III in which is mounted a valve eleby means of a yoke |8| with a lever 103, which ment ||2 having a fluted stem which is positioned in a bore in the body N0, the valve element ||2 being urged into engagement with a seat surroundingsaid bore by means of a spring 4 so'as to'control communication between the valve chamber Ill and a chamber. H6, which is connected by way of the pipe 45 with the unloading means associated with the compressor cylinder. The chamber is connected with the "engine inlet passage 9 by way of a pipe I20.

The casing section |||l has, in addition, a valve element |22 associated therewith'and having a fluted stem which is mounted in a bore in the body section ||0 which communicates with the chamber 6 and with the atmosphere. The

surrounding the bore in which the stem of the valve element is positioned so as to control communication between the atmosphere and the chamber H6, while the end of the stem of the valve element |22 is adapted to engage the end of the stem of the valve element 2.

'valve element |22 is adapted to engage a seat The valve elements 2 and |22 are operated rounded end portion I34 which is adapted to enage the face of the va-lveelem'ent |22.

The other end use of the lever I32 is forked so as to extend around the end of the plunger 96 whi h 1135 flat ,facesgl-35iormed thereonand-terminating in a shoulder 131;,- yvhich is adapted to en age. the iorkedgend. portion I3. of;the.lever 3 after a predet rm ed amount movem n seatand move-the valveelement II2. away; from its seat ject on one side to the pressure of the fluid in a chamber I46, which is constantly connected to I the force exerted by the fluid in the chamber I 46' against the spring I ;;-r

. The fluid pressureresponsive device I6 comprises a plurality. of casingsections including the sections I40, I4I and I42,- and is preferably mounted on the. side of the crank case portion of the body ofthe compressor I. I

A movable abutment in the form of a diaphragm I44 which is clamped between the easing sections I40 and MI is provided, and is subthe reservoir 4 by way of a passage and pipe 148.

Thediaphragm I44 is engaged o n the other side by a plunger I50 which is mounted in a bore in the casing section MI and which has secured thereto a stem I52. The plunger I50 is subject to the pressure of a spring I54 which presses against a plate I55, fitted against one face of the the compressor crank-case by way of a passage I6I, as is best shown in Fig. 3 of the drawings.

The casing section I42 has a bore I62 therein and has a seat rib I65 which surrounds a passage leading from the bore I62 to the chamber I60. A valve disc I61 is provided and is adapted to seat against the seat rib I65 being urged into engagement therewith by means of a spring I69 acting through a piston I68 which is mounted in the bore I62. 7 The' casing section I42 has a. passage I10 formed therein which communicates with the bore I62 at a point intermediate the valve disc I61 and the piston I68 when the valve disc is in position against the seat rib I65 and this passage communicates with the pipe 86 by way of-,a pipe The casing section I42 has a passage I13 formed therein which communicates with the bore I62 on the spring side of the piston I68 and with the chamber I and thereby with the crank case of the compressor. This permits lubricant which escapes past the piston I68 to the spring side of the piston to flow to the compressor crank case and prevents the building up of a pressure on the spring side of the piston which would interfere with movement of the piston.

The various parts of the system are shown in Fig. 2 of the drawings in the position which they assume when the equipment is idle, and the pressure of the fluid in the reservoir 4 is such that of the fluid pressure responsive device I6 is insufiicient to move the diaphragm I44 against the opposing pressure of the spring I54, with the result that the valve disc I61 will be urged against the seat rib I by the spring I69 acting through the piston I68.

. .11 ASithegcompressorrl"is idle the lubricant pump ;I 4; will not; supply any lubricant/,iunder; pressure surezwi'llz be developedin the :ichamber Qntrol'de'yice- J5, with the result that will; be .moved against the capmemspringw.95,-. acting throughithe plungn movementi of the plunger 35 60213138 d no pres tm itxonan which; it isshown in the drawings; the

throttle valve, I0 ;will.be move.d to theen'gineidling,

I the position, in which it is shown in.Fig;.2 of the drawings; the shoulder I 31 will i bemoved away from the forked end 136 of the lever I30, thereby permitting the. spring; M4 to movethe valve ele- 1 ment I;I2 into engagement with its seat and to -move; the valve element ,l22 out of engagement with its seat, thus; cutting off communication between the chamber. I I I and the chamber H6 and.

establishing communication between the chamber 3H6 and the atmosphere. This establishes communication between the atmosphere and the chamber 3I in the body 30 of the compressor inlet valve assembly I2 and permits the spring 36 to force the piston 32 downwardly so that the fingers 33 and 34 engage the annular rings 22 and 23 and move these away from the valve seat 2| against the springs 21, thereby unloading the compressor.

The engine 3 may now. be started and it will drive the compressor causing the crank shaft 52 to rotate. The engine 3 may be started very readily as the compressor will be unloadedat this time and will offer very little resistance to the operation of the engine during thestarting period.

On rotation of the crank shaft 52 of the compressor I the-piston 50 of the pump I4 will be caused to reciprocate inthe piston chamber 55; and at one point in its range of movement the lower end of the piston 50 is located above the inlet passage 10, and at another point in its range 6 of movement the-lower end of the piston is located below the inlet passage 10.

When the piston 50 moves to its upper position lubricant is drawn into the piston chamber 55 through the inlet passage 10, and when the piston moves downwardly'it cuts off the inlet passage 10 leading to the chamber 55 and the lubricant in the chamber 55 is placed under presber 55 is forced therefrom through the passage 15 and through .the choke 84 to the passage 85- which has the pipe 86 communicating therewith. In the event that the pump supplies an excess of lubricant over that required by the crank shaft bearings and that required by the control apparatus, and the pressure exceeds the desired value, lubricant will be released through the pressure regulating valve 16.

Lubricant which is supplied to the pipe 86 flows therethrough to the pipe "I and the passage I10, which leads to the bore I62 in the casing section which acts upon the valve disc I61 and tends 1 to hold this rib I65.

disc in engagement with the seat H 75 70 I42 of the fluid pressure responsive device I6, I I and establishes a fluid pressure in this bore,

Fluid which is supplied to the bore I62 through the passage I10 also acts upon the piston I68 and forces this piston to the right against the spring I69. The valve disc I61 will, therefore, be held against the seat rib I65 only by the fluid under pressure in the chamber intermediate the valve disc and the piston I68, but the pressure of this fluid is such that the force exerted by it on the valve disc I61 and tending to press the valve disc against the seat rib I65 is substantially greater than the force exerted on the valve disc I61 by the spring I69 when the valve disc is held against its seat by the spring.

Lubricant which is supplied to the pipe 86 also flows therethrough to the chamber I on the left hand side of the piston 9I, and on a predetermined increase in the pressure of lubricant in this chamber, the piston 9I will be forced to the right, as viewed in Fig. 2 of the drawings, against the spring 95 acting through the plunger 96, and, as the piston 9| is moved, the plunger 96 will also be moved and will move the lever I03 so as to move the throttle valve I0 from the idling position to the load position.

The volume of the chamber I00 on the left hand side of the piston 9| is preferably relatively large, and the rate of supply of fluid thereto through the choke 84 and the pipe 86 is preferably relatively small, with the result that a substantial time interval is required for a sufficient amount of lubricant to be supplied to the chamber I00 to effect movement of the piston 9| against the spring ,95 throughout the entire range of movement of the piston 9|, which is required to move the throttle valve from the idling position to the load position, thus insuring that the throttle valve I0 will be opened slowly. This permits the engine to accelerate slowly and smoothly.

After the piston 9| has been moved a predetermined distance from the position in which it is shown in Fig. 2 of the drawings towards the right, and thereby has efiected movement of the throttle valve I0 a predetermined amount from the idling position towards the load position, the shoulder I31 on the stem 96 will engage the forked end of the lever I30, and will cause this lever to pivot on the pin I32, with the result that the rounded end I 34 of the lever I30 will press upon the valve element I22 and force this valve element into engagement with its seat and will cause the valve element II2 to be moved away from its seat against the spring II4.

When the valve element I22 is moved into engagement with its seat communication is cut off between the chamber H6 and the atmosphere, and when, the valve element 2 is moved away from its seat communication is established between the engine inlet passage 9 and the pipe 45, which communicates with the chamber 3I in the inlet valve assembly I2 associated with the compressor cylinder.

A partial vacuum or region of reduced pressure will normally be present in the engine inlet passage 9, and a similar reduction in pressure will be effected in the chamber 3I, and, assuming that a degree of vacuum or that the extent of the reduction in pressure below atmospheric pressure is equal to or substantially equal to that which is present during normal operation of the engine, will cause the piston 32 to move upwardly against the spring 36, with the result that the fingers 33 and 34 will be moved out of engagement with the annular rings 22 and 23 and these will be moved to their seats by the springs 28, thus effecting loading of the compressor.

As a result of operation of the compressor I the pressure of the fluid in the reservoir 4 will increase, and a similar increase will be effected in the chamber I46 of the fluid pressure responsive device I6, which chamber is in constant communication with the reservoir by way of the passage and pipe I48.

When the pressure of the fluid in the reservoir 4 and in the chamber I46 increases to a predetermined value, the i'orce exerted by the fluid under pressure in the chamber I46 acting on the diaphragm I44 will be suflicient to move the diaphragm I44 and the plunger I50 against the spring I54, with the result that the end of the stem I52 will engage the valve disc I61, so that on further movement of the stem I52 the valve disc I61 will be moved away from the seat rib I65 against the pressure of the lubricant in the bore I62 acting on the valve disc, thus releasing fluid under pressure from the bore I 62 to the chamber I60, from which it flows by way of the passage I6-I to the crank case of the compressor I.

On the release of fluid from the bore I62 the pressure of the fluid acting on the valve disc I61 and tending to hold this valve disc in engagement with the seat rib I65 will be reduced with the result that movement of the diaphragm I44 will be opposed only by the spring I54 and thereafter the valve disc I01 will be very rapidly moved away'from the seat rib I65 by the stem I52 because of the reduction in the force opposing movement of the diaphragm I44. Fluid will thereupon be permitted to-flow very rapidly from the bore I62 and the connecting passage I and pipe IN to the chamber I60, and therefrom to the crank case chamber by way of the passage I6I.

The release of fluid under pressure from the passage I10 and the pipe I" results in a reduction in the pressure of the fluid in the pipe 86 and in the chamber I00 of the control device I5,

as the rate at which fluid is released from thebore I62 substantially exceeds the rate at which fluid is supplied to the pipe 86 through the choke 84.

Upon a reduction in the pressure of the fluid in the chamber I00 the piston 9I will be forced to the left by the spring 95 acting through the plunger 96, the'rate of movement of the piston 9| by means of the spring 95 being relatively rapid because of the relatively rapid rate at which fluid is released from the bore I62 past the seat rib I65.

On movement of the plunger 96 to the left, as viewed in Fig. 2 of the drawings, the throttle valve I0 will be moved from the load position to the idling position, while the shoulder I31 will be moved out of engagement with the forked end I36 oi the lever I so'that this lever no longer associated with the valve element I I2 presses onthe stem of the valve element I22 and moves this valve away from its seat.

On movement of the valve element II2 into engagement with its seat communication between on movementof the valve element I22 away from its seat.

When the chamber 3| is connected to the atmosphere the spring 36 forces the piston 32 downwardly so that the fingers 33 and 34 move the annular rings 22- and 23 away from the valve seat 2| against the springs 21 so as to effect unloading of the compressor.' 7 It will be'seen, therefore, that on an increase to a predetermined value in the pressure of the fluid compressed by the compressor, the control system operates to unload the compressor and to move the throttle valve from the load position to the idling position so as to reduce the speed of the engine which drives thecompressor.

The engine will'continue to drive the compressor, which will-not compress fluid into the reservoir 4 as the inlet valve is held in the open position, and upon a reduction in the pressure of the fluid in the reservoir 4 below a predetermined value, the pressure of the fluid inthe chamber I46 will be insufficient to maintain the diaphragm I44 against the spring I54 with the result that this spring will force the plunger I50 to the left until theplate I55 engages the casing section I4I. On movement ofthe plunger I50 to the left the stem I52 will also be moved to the left and will be moved out of, engagement with the valve disc I61, thereby permitting this disc to be moved into engagement with theseat rib I65 by the spring I69 acting through the piston I68 and cutting off the release of fluid from the bore I62 and the connecting passage I10 and 1 pipe I1I, past the seat rib I65 to the chamber I60, and therefrom to the crank case chamber of the compressor by way of the passage I6I.

' The diaphragm I44 will not be moved against the pressure of the fluid in the chamber I46 until I the pressure of the fluid in this chamber has reduced to a value substantially less than that which is effective to move the diaphragm I 44 to unseat the valve I61 as the diaphragm will not be moved to the right as viewed in Fig. 2 of the drawings, until the pressure of the fluidin the chamber I46 has increased to .a value such that the force exerted by the fluid acting on the diaphragm I44 is suflicient to overcome not only the spring I54, but also the force exerted by the fluid in the bore I62 acting on the valve disc I61 and tending to hold this disc in engagement with the seat rib I65 while the diaphragm l44 will not be moved to the left so as to permit the valve disc to seat until the pressure of the fluid in the chamber I46 has reduced to-a value such that the force exerted by the fluid on the diaphragm I44 is insufficient to hold the diaphragm against the spring I54 and. they relatively weak spring I Upon movement of the valve disc I61 into engagement with the seat rib I65 the fluid which is supplied to the pipe 86 by operation of the lubricant pump I4 establishes a pressure in the pipe 86 and in the chamber I 00ofjthe control device I5 causing the piston 9i to again moveto the right against the spring acting through the plunger 96, in the manner described in detail above, so as to again move the throttle valve I0 from the idling position to the load position, aifd to effect loading of the compressor so that the compressor again compresses fluid into, the reservoir 4. v

It will be seen that the control system provided by this invention provides means normally operative to'maintain the compressor unloaded,'together with means subject to and operated upon apredetermined reduction in the pressure of the fluid in the fuel inlet passage of the internal combustion engine employed to drive the compresso'rzfito actuate the unloading means to effect loading of the compressor.

Itwillbe seen also that the control system provided by this invention provides" means responsive to the pressureof the fluidcompressed by the compressor, and controlling the communication between the control means forthe unloading means and the fuel inlet passage of the driving engine. I

, In addition, it will be seen that the control system provides means responsive to the speed of the compressor and controllingthe communication between the engine inletpassage and the control means for the unloading means, so as to maintain the-compressor unloaded during starting.

It will be seen also that the system provided by this invention incorporates means responsive to the pressure of the fluid compressed and operative to move the throttle valve of the engine from the idling position to the load position, this movement being effected relatively slowly so as to give the engine an" opportunity to accelerate, and, in addition, has means to control the unloading means to effect loading of the compressor, this means being operable only after the throttle valve has been moved a predetermined distance from the idling position towards the load position.

While one embodiment of the control system provided by my invention has been illustrated and described in detail, it should be understood that the invention is not limited to these details of construction, and that numerouschanges and modifications may be made without departing from the scope of the following claims.

Having now described my invention, what I claim as new and desire to secure byLette'rs Patent, is:

1. In combination, an internal combustion engine having a fuel intake passage, and a throttle valve for controlling communication through said fuel intake passage, a fluid compressor driven by said engine and having unloading means associated therewith, control means for jthe unloading 'means comprising an abutment subject on one sideto the pressure of the fluid in a chamber, valve means controlling communication between .said chamber and the fuel intake passage, and means responsive to the pressure of fluid compressed by the compressor for controlling said valve means and for controlling the throttle valve. 1 t

2. In combination, an internal combustion engine having a fuel intake passage, and a throttle valve for controlling communication through said fuel intake passage, a fluid compressor driven by said engine and having unloading means associated therewith, control means for I the unloading means comprising an abutment subject on one side to the pressure of the.fiuid" in a chamber, valve means controlling communication between said chamber, and the fuel intake passage and means responsive to the speed of the compressor for controlling said valve means and the throttle valve. I

3. In combination, an internal combustion engine having a fuel intake passage, and a throttle valve for controlling communication through said fuel intake passage, a fluid compressor driven by said engine and having unloading meansassociated therewith, control means for the unloading means comprising an abutment subject on one side to the pressure of the fluid in a chamber, valve means controlling communication between said chamber and the fuel intake passage, and means responsive to the speed of the compressor and to the pressure of the fluid compressed by the compressor for controlling the said valve means and the throttle valve.

4. In combination, a fluid compressor having unloading means associated therewith, control means for the unloading means comprising an abutment subject on one side to the pressure of the fluid in a chamber, an internal combustion engine for driving said compressor and having a fuel intake passage, a throttle valve controlling the flow of fluid through said fuel intake passage, the throttle valve having an idling position and a load position, valve means controlling communication between said chamber and said fuel intake passage, and thereby controlling loading and unloading of the compressor, and means responsive to the pressure of fluid compressed by the compressor and operable upon a reduction in the pressure of the said fluid toa predetermined value to move the throttle valve from the idling position to the load position and to control operation of the valve means to effect loading of the compressor.

5. In combination, a fluid compressor having unloading means associated therewith, control means for the unloading means comprising an abutment subject to and operated upon-a predetermined reduction in the pressure of the fluid in a chamber on one side thereof, an internal combustion engine for driving said compressor and having a fuel intake passage, a throttle valve controlling the flow of fluid through said fuel intake passage, the throttle valve having an idling position and a load position, valve means controlling communication between said chamber and said fuel intake passage, means responsive to the pressure of the fluid compressed by the compressor and operable upon a reduction in the pressure of the said fluid to a predeterminedvalue to move the throttle valve from the idling position to the load position and to move the valve means to a position to permit communication between the chamber and the fuel intake passage and thereby effect loadingof the compressor, said valve means being moved to said position only after the throttle valve is moved to a point adjacent its load position.

6. In combination, a fluid compressor-having unloading means associated therewith, a lubricating system adapted to supply lubricant under pressure to said compressor, an internal combustion engine for driving said compressor, the engine having a throttle valve associated therewith for controlling the supply of fuel thereto, said throttle valve having an idling position and a load position, movable abutment means subject to and operated on a predetermined increase in the pressure of the fluid supplied thereto to move the throttle valve from the idling position to the load. position and to actuate the unloading means to effect loading of the compressor, means for supplying lubricant from the compressor lubricating system to said movable abutment means, and means responsive to the pressure of the fluid compressed by the compressor and controlling the pressure of the lubricant supplied to said movable abutment means.

7. In combination, a 'fluid compressor having unloading means associated therewith, aliquid circulating system operated in accordance with fuel supply device between an engine idling con- I dition and an engine load condition and for actu ating said compressor unloading means, yielding means opposing movement of said member to the position to adjust the fuel supply device to the load condition and toeffect loading of the compressor, movable abutment means operated on the supply of fluid thereto to move said member against said yielding means, and means subject to the opposing pressures of the fluid compressed by the compressor and of the fluid supplied to said movable abutment means and controlling the supply of liquid from the liquid circulating system to said movable abutment means.

8. In combination, a fluid compressor having unloading means associated therewith, a liquid circulating system operated in accordance with the speed of the compressor, an internal combustion engine for driving the compressor, the engine having a fuel supply device associated therewith for varying the quantity of fuel supplied to the engine, a movable member for adjusting said fuel supply device between an engine idling condition and an engine load condition and for actuating said compressor unloading means, yielding means opposing movement of said member to the position to adjust the fuel supply device to, the load condition and to effect loading of the compressor, movable abutmentmeans operated on an increase in the pressure of fluid supplied thereto to move said member against said yielding means, means for supplying liquid from the liquid circulating system to said movable abutment means at a restricted rate, and means subject to the pressure of the fluid compressed by the compressor for controlling the pressure of the liquid supplied to said movable abutment means.

9. In combination, a fluid compressor having unloading means associated therewith, a-liquid circulating system operated in accordance with the speed of the compressor, an. internal combustion engine for driving the compressor, the engine having a fuel supplydevice associated therewith for varying the quantity of fuel supplied to the engine, a movable member for adjusting said fuel supply device between an engine idling condition and an engine load condition and for actuating said compressor unloading means, yielding means opposing movement of said member to the position to adjust the fuel supply device to the load condition and to effect loading of the compressor, movable abutment means operated on an increase in the pressure of fluid supplied thereto to move. said member against said yielding means, means for supplying liquid from the liquid circulatingsystem to said movable abutment means at a restricted rate, and means subject to the opposing pressures of the fluid compressed by the compressor and of the liquid acting on said movable abutment means for controlling the pressure of the liquid supplied to said movable abutment means.

10. In combination, a mild compressor, an internal combustion engine for driving the compressor,.said engine having a fuel inlet passage, and unloading means for the compressor comprising a movable abutment subject to the pressure of the fluid in a chamber, said unloading means being operative to effect loading of the compressor on a reduction in the pressure of the unloading of the compressor on an increase in the pressure of the fluid in said chamber to a value higher than that present in the engine inlet passage when the engine is functioning in the normal manner.

11. In combination, a fluid compressor, an internal combustion engine for driving -the compressor, said engine having a fuel inlet passage,

and unloading means for the'compressor comprising a movable abutment subject to the pressure. of the fluid in a chamber, said unloading means being operative to efl'ect loading, of the compressor on a reduction in the pisessure of the fluid in said chamber substantially-to thevalue of the' fluid present in the engine inlet passage when the engine is operating in the normal manner, said unloading means being operative to efl'ect unloading of the compressor on an increase in the pressure of the fluid in said chamber to a i value higher than thatpresent in the engine inlet passage when the engine is functioning in the normal manner, and means responsive to the pressure of the fluid compressed by the compressor for establishing communication between said chamber and said engine inlet passage.

12. In combination, a fluid compressor, an internal combustion engine for driving the compressor, said engine having a fuel inlet passage, and unloading means for the compressor comprising a movable abutment subject to the pressure of the fluid in a chamber, said unloading means being operative to effect loading of the compressor on a reduction in the pressure of the fluid in said chamber substantially to the value of the fluid present in the engine inlet passage when the engine is operating in the normal manner, 'said unloading means being operative to effect unloading of the compressor on an increase a in the pressure of the fluid in said chamber to a value higher than thatpresent in the engine inlet passage when the engine is functioning in the normal manner, a lubricating system for supplying lubricant under pressure to said compressor, and means responsive to the pressure of the lubricant in said system for establishing communication between said chamber and the engine inlet passage.

13. In combination, a fluid compressor, an internal combustion engine for driving the compressor, said engine having a fuel inlet passage, and unloading means for. the compressor comprising a movable abutment subject to the pressure of the'fluid in achamber, said unloading means 'being operative to efiect loading of the compressor on a reduction in the pressure ofthe fluid in said chamber substantially to the value of the fluid present in the engine inlet passage when the engine is operating in the normal man- ,ner, said unloading means being operative to tioning in the normal manner, and means operative upon attainment of eflective speed by the compressor for establishing communication between said chamber and the engine inlet passage BURTON S. AIKMAN. 

